1. Field of the Invention
The present invention relates to a vehicle body rear structure.
2. Description of Related Art
Conventionally, a vehicle body rear structure which is provided with approximately a Y-shaped stiffening structure in plane view has been known. This is disclosed in, for example, U.S. Pat. No. 6,834,910. FIG. 6 is a bottom plane view schematically showing a conventional vehicle body rear structure as seen from a bottom side of a vehicle body.
As shown in FIG. 6, the stiffening structure is formed in approximately a Y-shape by a support member 109 and a pair of tension-compression bars 101 (tank lower frames). The support member 109 is disposed at approximately a center of a vehicle body B in a vehicle width direction, and extends in a front-rear direction of the vehicle body B. A rear end of the support member 109 is jointed to a cross support member 106 (rear floor end cross member), and a front end of the support member 109 is jointed to a receiving bracket 110. It is noted that the cross support member 106 is jointed to each rear end portion of the rear frames 102.
Each rear end of the tension-compression bars 101 is jointed to the receiving bracket 110 at a position close to a center of the vehicle body B, and each front end of the tension-compression bars 101 extending to each of side sills 105 in approximately the V-shape is jointed to the each of the side sills 105.
The vehicle body rear structure described above has a reinforced structure from the cross support member 106 disposed on a rear side of the vehicle body B to the side sills 105 disposed on the right and left sides of the vehicle body B via the support member 109, receiving bracket 110, and tension-compression bars 101.
However, in the vehicle body rear structure, the support member 109 has been disposed to be inclined downward from the cross support member 106 to the receiving bracket 110. Therefore, when a load upon a rear-end collision is input to the cross support member 106, there has been a possibility that the load may not be sufficiently transmitted to the receiving bracket 110 from the cross support member 106 via the support member 109. As a result, in the conventional vehicle body rear structure described above, it has been difficult to effectively disperse the input load into the receiving bracket 110, tension-compression bars 101, and side sills 105 via the tension-compression bars 101.
Therefore, for solving the above issue, the applicant had proposed a vehicle body rear structure having a spare pan frame which is horizontally disposed. This is disclosed in Japanese Patent Application No. 2006-238422 (not laid-open). FIG. 7 is a bottom plane view schematically showing a vehicle body rear structure having a spare pan frame which is horizontally disposed as seen from a bottom side of the vehicle body.
As shown in FIG. 7, the vehicle body rear structure includes a rear floor end cross member 206 which is bridged between each of rear frames 202 and jointed to the each of the rear frames 202, a rear floor cross member 210, and a middle floor cross member 203 which is located ahead of the rear floor cross member 210 and bridged between each of side sills 205 and jointed to the each of the side sills 205. In addition, the vehicle body rear structure further includes a pair of tank lower frames 201 and a pair of the spare pan frames 209.
Each rear end of the tank lower frames 201 is jointed to the rear floor cross member 210 at approximately a center in the vehicle width direction. Each of the tank lower frames 201 extents approximately in a Y-shape toward each side of the vehicle body B from the rear floor cross member 210, and each front end of the tank lower frames 201 is jointed to each of the side sills 205. The spare pan frames 209 extend between the rear floor end cross member 206 and rear floor cross member 210 in the font-rear direction of the vehicle, and jointed to the rear floor end cross member 206 and rear floor cross member 210. The spare pan frames 209 are arranged substantially horizontally between the rear floor end cross member 206 and rear floor cross member 210. It is noted that a fuel tank T is disposed in a space surrounded by each of the rear frames 202, rear floor cross member 210, and middle floor cross member 203, and the tank lower frames 201 are disposed beneath the fuel tank T.
In the vehicle body rear structure described above, a load upon a rear-end collision is transmitted to the side sills 205 via the rear floor end cross member 206, spare pan frames 209, rear floor cross member 210, and tank lower frames 201. In this case, since the spare pan frames 209 are arranged horizontally different from a case of the support member 109 (see FIG. 6) of the conventional vehicle body rear structure (for example, U.S. Pat. No. 6,834,910), the load is effectively transmitted to the tank lower frames 201 via the spare pan frames 209. As a result, the load is effectively dispersed in the vehicle body rear structure.
However, in the vehicle body rear structure, significant irregularities are formed on a bottom side of the vehicle body B by the rear floor cross member 210, tank lower frames 201, middle floor cross member 203, and the fuel tank T disposed in a space surrounded by the above members which are disposed on the bottom side of the rear portion of the vehicle body B. That is, although the vehicle body rear structure can improve a collision safety performance, an aerodynamic performance of the vehicle is decreased by the irregularities on the bottom side.
It is, therefore, an object of the present invention to provide a vehicle body rear structure which can improve both the collision safety performance upon a rear-end collision and aerodynamic performance of a vehicle.